[PATCH RFC 07/10] unwind/x86: Add HAVE_USER_UNWIND

[Josh Poimboeuf]

Use ARCH_INIT_USER_FP_FRAME to describe how frame pointers are unwound
on x86, and enable HAVE_USER_UNWIND accordinlgy so the user unwind
interfaces can be used.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 arch/x86/Kconfig                   |  1 +
 arch/x86/include/asm/user_unwind.h | 11 +++++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 arch/x86/include/asm/user_unwind.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cacf11ac4b10..95939cd54dfe 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -278,6 +278,7 @@ config X86
 	select HAVE_UACCESS_VALIDATION		if HAVE_OBJTOOL
 	select HAVE_UNSTABLE_SCHED_CLOCK
 	select HAVE_USER_RETURN_NOTIFIER
+	select HAVE_USER_UNWIND
 	select HAVE_GENERIC_VDSO
 	select HOTPLUG_PARALLEL			if SMP && X86_64
 	select HOTPLUG_SMT			if SMP
diff --git a/arch/x86/include/asm/user_unwind.h b/arch/x86/include/asm/user_unwind.h
new file mode 100644
index 000000000000..caa6266abbb4
--- /dev/null
+++ b/arch/x86/include/asm/user_unwind.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_USER_UNWIND_H
+#define _ASM_X86_USER_UNWIND_H
+
+#define ARCH_INIT_USER_FP_FRAME						\
+	.ra_off		= sizeof(long) * -1,				\
+	.cfa_off	= sizeof(long) * 2,				\
+	.fp_off		= sizeof(long) * -2,				\
+	.use_fp		= true,
+
+#endif /* _ASM_X86_USER_UNWIND_H */
-- 
2.41.0